The cardiac sphincter, also referred to as the lower esophageal sphincter (LES), is a valve found in the esophagus, the tube responsible for transporting foods and liquids to the stomach from the mouth. This particular valve is located just between the bottom of the esophagus and the stomach. A sphincter is a specialized type of muscle with an opening that relaxes and contracts, allowing this muscular valve to open and close as necessary. When this valve does not function properly, a variety of medical issues, including acid reflux or GERD, may occur.
The valve is in a closed position the majority of the time, and it opens only when necessary in order to allow food and liquid to pass into the stomach. This sphincter closes again once the food or liquid enters the stomach. Air pressure in the stomach can sometimes overcome this muscle, causing the person to belch, forcing the valve open in order to allow the excess air to be released.
If the cardiac sphincter becomes weak or damaged, it may not open and close at appropriate times. This often causes the contents of the stomach, including stomach acid, to go back through the sphincter into the esophagus. When this happens, a condition known as GERD often occurs. GERD stands for gastroesophageal reflux, and there are a number of uncomfortable symptoms associated with this condition.
Common symptoms of GERD include heartburn, indigestion, and swallowing difficulties. Heartburn is a painful, hot feeling that generally starts in the middle portion of the chest and often moves closer to the throat. Indigestion occurs when there is an acidic or sour taste in the mouth. Swallowing difficulties can include an overwhelming feeling that something is stuck in the throat as well as a sensation of choking.
When the lower esophageal sphincter does not function properly, a medical professional may prescribe medications to help reduce stomach acid, relieving some of the painful symptoms of GERD. Dietary changes may also be advised, as some foods, particularly those with high acid content, have been known to intensify the symptoms. On some occasions, surgery may be recommended in order to repair any damage to the valve. Surgery is particularly useful if a hiatal hernia has developed due to the sphincter's dysfunction. A hiatal hernia is a medical condition in which part of the stomach protrudes through a hole that has developed in the abdominal wall, often due to acid reflux or GERD.